1. Field of the Invention
The present invention relates to novel mixtures of different alkoxylated ether sulfate anionic surfactants based on plasticizer range linear or branched alcohols, and to concentrated aqueous surfactant compositions based on such mixtures. More particularly, this invention relates to certain novel relatively short chain ether alcohol sulfate anionic surfactants produced by propoxylation or butoxylation of "plasticizer" range primary or branched "oxo" alcohols, optionally followed by alkoxylation with ethylene oxide or with a mixture of ethylene oxide and propylene oxide or butylene oxide, followed by sulfation and neutralization. The compositions of the invention are prepared as concentrates containing high proportions of active ingredients which are capable of being diluted with water without formation of a gel phase or lumps and as surfactants exhibit properties comparable to commercial surfactants prepared from "detergent" range alcohols.
2. Description of the Prior Art
During the last several years, primary "detergent" range alcohol (i.e. fatty alcohol) ethoxylated sulfates have been used extensively in large volume surfactant applications such as light duty liquid dishwashing detergents, concentrated laundry detergents, hard surface cleaners, and as textile surfactants. The advantages of the ethoxylated ether sulfates over the previously employed alcohol sulfates include ready synthesis, increased solubility, and insensitivity to hard water (see for example T. P. Matson, Soap and Chemical Specialties, November 1963).
Propoxylated and butoxylated alcohol ether sulfate anionic surfactants have been disclosed in the prior art, but are not known to have been employed in commercial applications. A substantial portion of prior art disclosing such surfactant compositions deals only with "detergent" (i.e. containing about 12 to 18 carbon atoms) as disclosed, for example, in Weil et al. U.S. Pat. No. 4,383,706, and with short oxypropylene chains generally between about 1 and 3 propylene oxide units, as disclosed for example in Tuvell et al U.S. Pat. No. 3,775,349. Although 8 and 10 straight chain carbon alcohols containing greater than 3 oxypropylene units have been studied, J. Chlebicki et al, Synthesis and Surface Activity of Sodium Polyoxypropylated Higher Alcohol Sulfates", Tenside Detergents, 17, 130-134, (1980), the authors conclude that these materials are generally inferior surfactants as compared with propoxylated surfactants prepared from "detergent" range alcohols.
Fabric softeners employable in the laundry wash, rinse or dryer cycle are desired for commercial application. Furthermore, because of the inconvenience of rinse and dryer cycle application, the industry is attempting to develop softeners that are compatible with wash cycle applications. Cationic quaternary ammonium salts, which are used commercially in fabric softening applications, cannot be used in the wash cycle with anionic surfactants. It is believed that the cationic and the anionic materials complex and precipitate, thus reducing detergency. Although wash cycle detergent/fabric softner formulations have been prepared from non-ionic surfactants and cationic softeners, these formulations lack the detergent power that can be obtained when an anionic surfactant is used as the detergent.
Mixtures of surfactants have also been prepared and sold for a wide variety of industrial and domestic applications. Such compositions often are required in fluid form, and it is desirable that they should contain as high a proportion of active material as possible, in order to reduce the cost of storage and transport. However, in the case of most surfactant mixtures, it has generally been impossible to obtain a fluid composition to concentrations above about 30 to 50 percent and higher, by weight, of active ingredient, and further, depending upon the nature of the mixture, small amounts of water, i.e. up to about 10 percent may depress the melting point slightly while larger quantities of water result in the formation of a rigid gel rather than a fluid solution as a result of a phase change. Hence, it has generally been found that as the total concentration of surfaces active ingredient in a dilute solution approaches a critical level, which usually ranges between about 30 to 50 percent by weight or higher, the viscosity of the solution begins to rise, causing difficulty in preparing and handling the solution. At the critical level the solution sets into an immobile gel or phase separation occurs.
It has sometimes been possible to increase the concentration of active ingredient by addition of viscosity modifiers or co-solvents, such as alcohols, which act as thinners thereby lowering the viscosity of the solution and inhibiting the formation of gels, and permitting the obtainment of higher concentrate solutions. However, such co-solvents are normally effective in producing substantial increases in the attainable concentration when they are present in readily large quantities, which solvents, at these concentrations, constitute a fire hazard and may adversely affect the properties of the product compositions for many of its desired end uses and/or increase the cost of the product.
As used herein, the term "active concentration" will be used to denote the total concentration of "active" i.e., surface active, ingredients in the aqueous anionic surfactant composition.
Aqueous solutions of sulfates of alkoxylated fatty alcohols, generally containing from 10 to 24 carbon atoms in the alcohol chain, such as sulfated ethoxylated lauryl alcohol, or mixtures containing lauryl alcohol derivatives, have been employed in cosmetic, toiletry and other detergent compositions. In general, these compositions are supplied at about 30 percent active ingredient, but in the interest of economy and transport and packaging, high concentrations of the order of 50 to 70 percent, are also commercially available. At these high concentrations they have the texture of a thick paste. In the final formulation, these compositions are normally present in an amount of less than about 30 percent active ingredients in aqueous solution. As indicated above, unfortunately, upon dilution of these concentrates with water, rather than the viscosity diminishing as might be expected, the viscosity begins to substantially increase; for example, the sodium salt of the sulfate of a di-ethoxylated derivative of a commonly used mixture of alcohols containing between 10 and 18 carbon atoms having a concentration of 60% active matter, the balance being water, has a viscosity of approximately 17,000 centipoises. Upon dilution to 45% active matter, the viscosity increases to greater than 500,000 centipoises. Upon further dilution, the viscosity drops until at the concentration used in shampoos, for example, it again becomes liquid.
Although it has been possible in some instances to employ such concentrates without the incorporation of viscosity modifiers, such as increase in the viscosity during dilution, naturally contributes substantial problems for the formulator. Such problems include the formation of lumps and gels which are themselves only difficulty soluble on attempted further dissolution. In order to avoid these problems, viscosity modifiers have been incorporated as above indicated, in aqueous concentrates of sulfates of ethoxylated fatty alcohol so as to maintain viscosity of the solution at high concentrations at a level such as to maintain the viscosity at a level such that the solutions are reasonably free flowing and are easily diluted through any required concentration. In addition to modifying the viscosity of these solutions, it is also necessary that any additive employed should not prevent or hinder the effect of thickeners conventionally used, such as sodium or ammonium salts, which may be incorporated in the finished formulation in order to provide an acceptable consistency. At present, this problem is being reduced by incorporating into the concentrated aqueous sulfate of ethoxylated fatty alcohol, an alcohol of low molecular weight such as isopropranol or ethanol. However, the use of such alcohols is disadvantageous in that having high vapor pressure their odor is detectable in the finished formulation and, further, such compositions may constitute a fire hazard as above indicated.
An object of the present invention is to provide aqueous solutions of admixtures of anionic surfactants based on plasticizer range linear or branched alcohols.
A further object of the present invention is to provide water and organic solvent soluble anionic surfactant admixture compositions characterized as being free of unpleasant odor and exhibiting excellent detergency and stability in hard water and low foaming properties.
Another object of this invention is to provide highly active concentrated anionic surfactant, free-flowing admixture compositions requiring no added solubilizing agents and which are capable of being diluted with water without formation of undesired highly viscous lumps or gel phase.
Other objects of this invention are readily apparent to those skilled in the art from the following description.